6HP 2 cycle Yamaha Cooling Problem

"No water comes out of the tub

"No water comes out of the tube under the head when the engine is hot. I have checked all areas for water flow, changed the impeller even though the old one looked functional, and changed the thermostat. I think that the internal cooling passages are blocked?? It had been run in salt water before I got it. I am trying to make it work properly. Any suggestions on how to verify this or check that they are clear, and how to clear them if they are plugged?
Thanks for any help.
Bill"

Drop your l/u and take an air

Drop your l/u and take an air chuck and blow through the water tube. If blocked crack your therm housing open see if air is comming out there if so close therm blow through the tube under belly pan if no air comes try cleaning out the tube under the pan with a paper clip. If that doesnt work your probebley going to have to pull you powerhead and blow through your passages and through each tube the one to the l/u and through the other. Have had to junk a few 3hp yamaha's due to the blocks being cloged thats about all u can due that i know of.